Establishing a No-Lose Theorem for NMSSM Higgs Boson Discovery at the LHC

TL;DR

The paper investigates whether the NMSSM Higgs sector can be observed at the LHC under LEP2 constraints, by scanning a large NMSSM parameter space where decays to other Higgs bosons and SUSY particles are kinematically forbidden. Using NMSSM-corrected predictions for nine Higgs-detection channels and combining data from ATLAS and CMS at $L=300~\mathrm{fb}^{-1}$, the authors show that including $WW$-fusion modes eliminates the previously found ‘no-discovery’ regions, yielding $N_{SD}$ well above the 5-sigma threshold for all scanned points. They provide detailed bench marks illustrating the mechanism behind difficult cases, showing that strong Higgs mixing and near-degenerate Higgs masses can suppress multiple channels, but $WW$-fusion channels typically compensate. The work supports a no-lose theorem for NMSSM Higgs discovery at the LHC within the specified assumptions and underscores the importance of extending discovery modes (including LLPs and SUSY channels) to cover all parameter space.

Abstract

We scan the parameter space of the NMSSM for the observability of at least one Higgs boson at the LHC with $300\fbi$ integrated luminosity, taking the present LEP2 constraints into account. We restrict the scan to those regions of parameter space for which Higgs boson decays to other Higgs bosons and/or supersymmetric particles are kinematically forbidden. We find that if $WW$-fusion detection modes for a light Higgs boson are not taken into account, then there are still significant regions in the scanned portion of the NMSSM parameter space where no Higgs boson can be observed at the $5σ$ level, despite the recent improvements in ATLAS and CMS procedures and techniques and even if we combine all non-fusion discovery channels. However, if the $WW$-fusion detection modes are included using the current theoretical study estimates, then we find that for all scanned points at least one of the NMSSM Higgs bosons will be detected. If the estimated $300\fbi$ significances for ATLAS and CMS are combined, one can also achieve $5σ$ signals after combining just the non-$WW$-fusion channels signals. We present the parameters of several particularly difficult points, and discuss the complementary roles played by different modes. We conclude that the LHC will discover at least one NMSSM Higgs boson unless there are large branching ratios for decays to SUSY particles and/or to other Higgs bosons.